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Filed July 28, 1943 jglgja.

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Edgar Ljdar/d J0 5 I grana/www4' Patented Apr. 22, 1947 CAP Albin H. Warth and Edgar Lidard, Baltimore, Md., asslgnors to Crown Cork & Seal Company, Inc., Baltimore, Md., a corporation of New York Application July 28,1943, Serial No. 496,506

Claims.

This invention relates to caps and particularly center spot caps which include a metal shell. a

cushion liner disposed therein and a facing layer of resistant material united to the cushion liner in centered relation by a stratum of adhesive. The center spot protects the contents of the container from contact with the liner and permits the lip of the container to engage directly the cushion liner and thereby form a tight seal. In addition to the usual spots and overall facings of paper and metal foil, such as aluminum, caps in accordancel with this invention are formed with spots and overall facings from two sides Varnished paper discs, punching out a spot and centering the same -in adhered relation upon the cushion liner under simultaneously applied heat and impact pressure upon the cushion liner, and then subjecting the assembly to mechanical pressure. The pressure may be accompanied by heat, if desired, but we prefer a mild heat such as heat below 160 F. The

use of a single heating step and a single pressure step constitute a marked improvement, in that cushion liners having a waxed surface which, like two sides varnished paper or foil, has been regarded as adhesive repellant and hence unsuitable for spot caps. Of equal importance, spots having adhesive repellant surfaces, vsuch as two sides taining the spooled material under refrigerated conditions. In other words, under normal temperature and pressure conditions, offsetting, i. e., adhering of the convolutions of thespool during storage occasioned by a lack of heat and pressure stability of the adhesive coatingis precluded by the material of this'invention, and the strip freely unwi'ncis when acted on by the feeding mechanism -of the cap spotting apparatus. Refrigeration of the spool during storage is unnecessary. More= over, peeling or separating of the adhesive from the backing does not occur under the severe con dition of being associated with high gloss or generally considered adhesive repellant surfaces. To produce the cap embodying the facing material of the present invention, there may be used a new method of spotting which is more rapid and economical than present practice, and enables more comfortable conditions to be established for new method consists in preheating the cushion (1) the punch and presser plunger are cold, i. e., unheated and at atmospheric temperature, al though the latter may for some purposes be slightly warmed and (2) post heaters and pressure dials conventionally employed after the pressing step no longer are necessary. Moreover, the elimination of additional heating steps enables such advantageous materials as vinyl resin or chlorinated rubber, which are damaged by heat, to be successfully used as spotting materials.

In addition, the invention provides a new permanently thermoplastic and stable adhesive, having a high softening or tacking point which is useful in carrying out the improved method oi spotting just described and particularly allows materials and coated liners, heretofore regarded as adhesive repellant and, therefore, unsatisfactory for making spot caps, to be successfully used for cap spotting and liner purposes. The adhesive composition consists of a resin, wax. and an elastomer selected from the group consisting of v very important property of increasing adhesion y of the adhesive surface on aging, i. e., the adhesive increases in adhesive strength at a measurable rate from week to week. Moreover, the adhesive greatly increases its adhesion to the cushion discs when/caps are applied to bottles by crowning equipment.

A. preferred resin is Nevillite No. 3, which is vdescribed by the Neville Company of Pittsburgh as Cycloparafiin or naphthene polymers and is -a water white resin referred to as a cumar-indene resin. It is not adaptable of itself to form a iiex ible lm, but with the rubber or wax, or both, a desired continuous flexible llm of adhesive is produced. This adhesive resin is unsaponiable, permanently thermoplastic, water, alcohol, acid. and alkali resistant, resistant to salts, oxidation resistant, non-toxic, and freefrom objectionable odor or taste. The resin is resistant to polar solvents, but soluble in hydrocarbon solvents and in most of the solvents for wax and rubber. The resin is also cheap, easy to handle, compatible with mineral oil, paraiiin, wax, petrolatum, rubber, Vistanex and other resins, such as hydro= genated rosin, Araclor resins and methacrylate resins which may be mixed with the Nevillite.

Particularly, the resin has a high` softening point (224 F. to 228F.) and a high melting point (293 F to 301 F.), and unlike many other resins,

in subdivided form, its microscopic particles do not fuse or coalesce together under normal tem-4 peratures or spooling or handling pressure, or upon warming, while the composition is aging, i. e.. in storage, so as to become tacky and there- 'by produce offsetting ofthe rolled spot material. The Various properties outlined make the resin an ideal component of the adhesive, particularly its high softening point which assists in maintaining the composition permanently thermoplastic and stable on the one hand, while affording optimum adhesiveness under heat on the other. In this connection, the high softening and melting point of the resin assists in preventing offsetting of the adhesive composition to bind the convolutions of the spool of the strip spotting material under normal temperature and pressure conditions and when stored prior to use, and prevents decomposition by heat during the spot assembly operation.

The wax employed has a high melting point,l1 e. g., about 185 F. It is freely soluble in the hydrocarbon solvent when warm, but after coating and drying precipitates on cooling to normal room temperature and is compatible with the high softening point resin and rubber. When the adhesive composition is dried, the Wax aids formation of the film and tends to bloom out on the film surface. The wax is of an amorphous or micro-crystalline parafiinic character containing its natural oils, which increases adhesiveness. Moreover, the wax has optimum adhesiveness when warm, a higher tenacity than lower melting point waxes, and by having a high melting point,

raises the melting point of the composition. This wax very substantially aids in eliminating olfsetting of the adhesive on the spooled strip spotting material.

The rubber has the function of a film forming constituent and also iniiuences the tacking point, and the use of reclaim rubber affords a softer and more adhesive composition and acts as a carrier for the resin and the wax. It assists in producing a heterogeneous composition of the crepe rubber and the other constituents.'

A suitable exemplary adhesive composition contains substantially the following:

Crepe rubber grams 350 Ivorylite (reclaim) do 75 Pale yellow (petrolatum) wax 185 M. P do 75 #3 Nevillite resin do 1,165 Rubber-Sol (end point 24S-265 F.) quarts-- 8 Instead of Rubber-sol, we sometimes use Benzo-sol, about eight quarts, and varnoline, about one quart.

. This composition is formed by breaking down the crepe rubber in a mill and then milling in the While we prefer a "Nevillite resin," such as No.

3, Nevillite No. 1 and No. 2 may be instead emticular the W grade (The Pennsylvania Industrial Chemical Corporation), and methacrylate `(Du Pont) resins, having properties substantially similar to Nevillite. The latter mentioned resins, however, do not compare favorably in properties with a "Nevillite resin, and although they may be used with the latter, they are not required. They are, however, compatible with rubber and wax.

The pale yellow Wax referred to in the above example is an adhesive wax of high melting point and is regarded as amorphous or micro-crystal-v line paramn. This yellow wax may also be defined as petrolatum Wax, being one of the amorphous or micro-crystalline paraflin waxes produced by several of the oil refiningv companies from oil residuums. Other waxes may be used providing they have the desired adhesive, high .melting point, and other characteristics recited.

Instead of a mixture of reclaim and crepe rubber, we may use Vistanex, although it is not preferred except in admixture with the crepe and reclaim rubber or as a substitute for one or the other. Nevillite resin and wax, and requires no particular change in solvent. Para rubber, smoked sheet, and other rubber or rubber-like materials may be used Wherel odor, taste, and impurities are not objectionable.

The solution formed as described is coated upon the spotting material of paper, foil, chlorinated rubber, polyvinyl acetal resin, and vinyl resin,v

or to the under surface of a facing of paper or other flexible material having an exposed surface film of such rubber or resin, being applied like a varnish with a coating roll as is the practice with other adhesives. The coating is applied in suiiicient quantity to give a dried continuous film thickness of about .0002 to .0003 on the material. tageous, in that it allows the spot to be substantially flush with the surface of the liner. The material is dried ata temperature of about 175 F. to 200 F. and can be coated and dried at the rate of feet or more per minute in an oven 80 feet long, although the length of the oven may be changed with design. When the spot material is coated as just described, it is wound up into tight rolls which are slitV to the proper width for the spools which are to be attached to the spot crown assembly machine. It is extremely vimportant that there be no offsetting of the thermoplastic adhesive, for if such occurs, the material cannot be freely unwound.Iv As explained above, the type of wax and resin employed contributes substantially to eliminate offsetting and particularly the Wax acts to preclude this objectionable effect. In fact, when the adhesive is drying, the wax tends to bloom out in the lm.

At about F. the adhesive or cement iilm becomes tacky under pressure of the punch, and

the cement increases in tackiness up to about F. In spot machine operations, theheat is applied to the adhesive preferably at the instant of assembly of the spot with the cushion disc, and

Vistanex is compatible with both This thin coating is advanmake it very tacky; such melting or free fluidity temperature approximating about 235 to 240 F. 'Ihe adhesive composition is a heterogeneous mix' ture which will start to soften slightly above substantially 170 F., e. g., at172 F. and become more and more uid up to about 240 F. At 172 F., the slightly softened, but still somewhat tacky adhesive will form a strong union if the adhesive is cooled or only partially cooled during application of pressure. The tacking point of substantially 170 F. is the beginning of the softening point, and as the cement continues to become more and more soft up to the melting pointof 235 F., it may be'stated that the tacking range is; between 160 F. and above substantially .170 F., e. g., 172, and the softening range between above substantially 170 F. and 235 F. When coated upon the spotting material, the tacking temperature is somewhat reduced upon application of positive pressure as, for example, when the punch plunger deposits the spot upon the heated cork composition or other liner.v This pressure responsiveness is likewise present when the pressure plunger engages the spot, after it has been positioned, to permanently adhere it to the liner. Under normal temperatures, however, the adhesive or cement does not fuse or become tacky, and likewise under pressures present in the spool or occasioned by handling, there is no offsetting tendency. This is important, as explained heretofore, in allowing the strip material to be freely unwound from the spool atall times and in no longer requiring that the strip material be refrigerated during storage, particularly where the temperature within the plant is high, or in the summer time. The hardened adhesive composition forms a permanent stable union between the spot and the cushion liner which is not affected by temperature changes, -such as are present under sterilizing and pasteur-loing conditions to which the sealed container may be subjected. In this connection, while sterilization temperatures of 212 F. may soften the adhesive composition, it does not flow, and the union between the facing and liner is not impaired. The composition hardens as soon as cooling takes place and again exerts its maximum adhesive effect. i

Where rubber in crepe or reclaim, or both, is not available, we have found it practicable to use so-called synthetic rubber, for example, the Buna S type and the butyl. Compositions including these synthetics have a somewhat lower tacking point than scribed, but have substantially the other advantageous characteristics.

When Buna Sis employed to replace the rubber in part, a formula such as the following has been found to be satisfactory:

'the adhesive heretofore de- Pounds 187 (petrosene A. m.

advantages of the adhesive previously Butyl rubber Micro-crystalline wan 167 F.) 50 Black pitch SHV 8 4 23 P-25 cumar resin 50 Piccolyte El-125 470 rotar Seuss 'zoo `'Total solvents (Benzo-Sol) 1450 Butyl rubber is a copolymer of isobutylene and 2 to 5% of other unsaturated hydrocarbons such as butadiene or isoprene. k

Piccolyte .Si-125 is atherrnoplastic hydrocarbon terpene resin having a melting point of about 257 F., manufactured by Pennsylvania Industrial Chemical Corporation of Claireton, Pennsylvania.

AThe black pitch in the above formula increases the viscosity of the adhesive, and is found desirable when butyl rubber is the principal ingredient. An adhesive produced from this lastmentioned formula coated upon foil or paper for facing container closures has a tacking point of from about 14u-150 F., and the minimum mentioned is appreciably in excess of the ordinary gutta percha heretofore used. It has also been found that the tacking point of the butyl increases with age as the paper or foil is stored.

, case as a crown cap having the usual Grams Buna S 385 180 F. M. P., yellow wax.` 66 Ruby black reclaim rubber 66 Nevindene R-l resin 23 Piccolyte S125 resin 1020' 'rotaisolids 1560 'rotar savent 4680 Total amount cement 6240 Compositions such' as the foregoing will be found to have a tacking point from about to F., which is substantially higher than the tacking point of gutta percha which has heretofore been widely used. and, therefore, has the vwith all types of caps.

Referring to the accompanying drawings:

Figure 1 is a sectional View of a metal foil, paper, chlorinated rubber, vinyl resin, or other laminated material forming the spot facing provided with an adhesive coating before it is adhered to the cushion liner;

Figure la is 'a similar view showing a two sides varnished spot or overall' facing material;

Figure 2 is a sectional view showing a center spot adhered to a cushion liner of cork composition having a Wax coating;`

Figure 3 i's a sectional view showing an overall faeing adhered to a cushion liner of cork composition; and

Figure 4 is a diagrammatic view showing the method of applying spots to caps in accordance with this invention.

Referring to Figures 2 and 3, the ca'p comprises a metal shell I0 illustrated in the present crimped skirt il, but the invention is equally applicable Disposed within the shell is a cushion liner I2 of composition cork to which the spot or overall facing I3 of paper, metal foil, such as aluminum foil, chlorinated rubber, vinyl resin, or other'suitable material is adhered by a stratum of adhesive I4. While we have shown and described a liner of cork composition, natural cork prepared in accordance with the patent to Mueller, No. 2,147,987, February 21, 1939, may be employed, as well as liners of paper, rubber, and other materials.

In Figure 1a, we have shown a spot of paper,

foil, or other material ycoated on each side with,

varnish I5 for use as a facing in accordance with Figures 2 and 3. In Figure 2, the liner surface is coated with a lm of wax 'I6 which in some cases is highly advantageous, to which facings of the character shown perature of about 160 i which impacts upon the 7 in Figues '1, 1a, and 3 may be applied.

Referring to Figure 4, strip spotting material I3, I4 is continuously fed from the spool I1 to the punch I8, where a center spot I3 is punched out over the cushion disc I2 and deposited by the punch plunger upon the cushion liner disposed in the shell I0. A plurality of shell cushion assemblies are continuously and progressively fed first to a heating means I 9, such as a gas name, which heats the surfaces of the cushion discs to a temperature of substantially the tacking point or point of maximum adhesiveness of the adhesive. the present case, the tacking point of the cement composition I4 is between substantially 160 F. and above substantially 170 F., i..e., it forms a strong union at 172 F. as above described. A tem- F. to above substantially 170 F., e. g., 172 F. may be considered the average tacking point for cap spotting purposes, in view of the pressure which in the next continuous and progressive operation is imparted when the punch plunger I 8 severs and deposits a spot in centered relation upon the heated cushion liner. The adhesive mixture which at ordinary atmospheric pressure will soften slightly at above 170 F. and continue to soften at increasing temperatures. Under applied pressure the adhesive composition becomes tacky and adhesive at a temperature somewhat below its softening point so that if the adhesive is somewhat softened it will form a strong union s if the adhesive is cooled or partially cooled during application of pressure. The punch plunger I8 is at atmospheric temperature, i. e., cool. The

Inv

composition is a heterogeneous tackiness of the thermoplastic adhesive produced by contact with the heated surface of the cushion liner causes the spot to be initially and strongly attached to the cushion liner, whereupon for the third operation, each assembly is continuously progressively passed to a pressing plunger 20 spot and permanently unites the same to the liner. 'The pressure plunger exerts suiiicient pressure or impact to assure that the warmed adhesive will have its maximum adhesiveness notwithstanding the surface of the cushion, may have cooled slightly, by reason of its travel from the heating means I9. 'I'he plunger 20 is cool, i. e., at atmospheric temperature, but on occasion may be warmed. It will be noted that the method. of forming spot caps embodies only three spotting steps, namely, heating the cushion liner, depositing the spot thereon w h heat and pressure, and then permanently pressing the spot upon the cushion liner. After the caps leave the press, the adhesive hardens at normal temperatures and the use of further heating or pressure steps is unnecessary.

This application is a continuation-impart of 4our copending application Serial No. 346,846, filed July 22, 1940 and of our copending application Serial No. 391,599, filed May 2, 1941, which is now Patent No. 2,367,250, dated Jan. 16, 1945.

We claim:

1. A cap having a metal shell, a cushion liner therein, and 'a facing adhered to the liner by a stratum of adhesive composition comprising essentially a resin, a waX, and rubber, the resin being present in substantially higher percentage than the wax and rubber combined, the composition having a tacking point only within the range of from about F. to about 172 F.

2. A cap according to claim 1 wherein the facing is varnished paper.

.3. .A cap according to claim 1 wherein the facing is metal foil.

4'. A cap according to claim 1 wherein the facing isvinyl resin.

5. A cap according to claim 1 wherein the resin is a hydrocarbon terpene resin having a melting point of about 257 F., the wax is a microcrystalline wax having a melting point of about 167 F. and the rubber is a copolymer of isobutylene and 2 to 5% of other unsaturated hydrocarbons.

t ALBIN H; WARTH.

EDGAR LIDARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

